The odds that an offender with relatively low anterior cingulate activity would be rearrested were approximately double that of an offender with high activity in this region, holding constant other observed risk factors. These results suggest a potential neurocognitive biomarker for persistent antisocial behavior.

However, using ACC activity as a dichotomous variable misclassified 40% of low ACC participants who did not reoffend and 46% of high ACC participants who did commit crimes after release, not exactly the odds you'd want for making parole decisions. Even the senior author was doubtful that an fMRI test would ever be useful for risk assessment purposes on a case by case basis.

Since Aharoni and colleagues made their individual subject data available as supplementary material (Download Dataset_S01, XLSX), I was interested in how some of the demographic and performance variables might be related to recidivism, since these are obviously cheaper and easier to collect from incarcerated prisoners than MRI scans.

The cognitive task performed during the fMRI experiment required responding to a frequent stimulus presented 84% of the time ("X") and inhibiting responses to a rare stimulus ("K").

The study compared brain activity on incorrect responses to "K" (commission errors) and correct responses to "X" (hits) in a region of interest in the dorsal ACC, which has been implicated in error processing (Simons, 2010), among manyotherthings. The authors framed the results largely in the context of impulse control, but other explanations are possible (as we'll see later).

Are any of the task performance variables related to recidivism? Starting with some very simple-minded t-tests, the rate of commission errors in the group of participants arrested for nonviolent offenses1 (n=40) did not differ significantly from what was seen in those not arrested again (n=56).2

Data from (Aharoni et al., 2013). Commission errors in the Go/NoGo task (% incorrect responses on NoGo trials) and omission errors (% missed responses on Go trials) for inmates that went on to commit nonviolent offenses within 4 years after release (Nonviolent) and those that did not (None). The trend for the reoffenders to commit more errors was not significant (p=.09) even without correcting for multiple comparisons.

Although there were data from a large control group of nonoffenders (n=102) used to set the ACC ROI, we don't have their behavioral results. I consulted an earlier fMRI paper by Kiehl et al. (2000) that used a very similar Go/NoGo task in 14 control participants. Commission errors occurred on 23.7% of NoGo Trials and omission errors on 3% of Go Trials, which is similar to what was seen in the offenders (overall means of 25.04% and 3.44%, respectively).

Reaction times (RTs) did not differ between the two offender groups either, suggesting there wasn't a differential speed-accuracy tradeoff (e.g., if the reoffenders were slower yet making marginally more errors).

Data from (Aharoni et al., 2013). RTs in milliseconds for commission errors (incorrect responses on NoGo trials) and hits (correct responses on Go trials) for inmates that went on to commit nonviolent offenses within 4 years after release (Nonviolent) and those that did not (None). There were no group differences.

Surprisingly, RTs were slower on commission errors (358 ms) than on hits (346 ms), a small but highly significant difference (p=.0005). This is the opposite of what you'd expect if the errors were due to impulsive responses. If the participants were becoming careless and not fully evaluating the NoGo stimulus, they'd be faster on error trials. This is why I'm not convinced the ACC activations are entirely related to behavioral impulsivity. In EEG studies of error processing, the degree of ACC activity3 is related to the emphasis placed on accuracy (Gehring et al., 1993), so if the reoffenders didn't care as much about accuracy, this could account for their low ACC status. One interesting bit of data for the authors to examine would be RT and accuracy on responses following an error, which indicates the amount of behavioral adjustment after making a mistake. Did the reoffenders show a lower propensity to slow down and become more careful? If so, this might reflect a lack of concern about the consequences of their actions.

However, the most puzzling thing to me were scores on Factor 2 of the Psychopathy Checklist-Revised (PCL-R) (Hare, 2003). Factor 2 is thought to reflect impulsivity, stimulation seeking, and irresponsibility (Ermer et al., 2012). The rearrested and not-rearrested groups were significantly different as expected, but in the opposite direction (unless I'm missing something here) — scores were lower in the group that was rearrested, in comparison to those who were not (p=.001).

Data from (Aharoni et al., 2013). Beta-weights from the dACC region of interest and a control region in medial prefrontal cortex (mPFC). PCL-R f2 is score on Factor 2 of the Psychopathy Checklist-Revised, normalized using a log transform (p=.001).[ROIs and PCL-R not measured using the same units, obviously.]

In the paper, Aharoni and colleagues noted that age at release and Factor 2 scores showed predictive effects along with ACC activity. This was only when nonviolent crimes were considered [remember that only nine participants were arrested again for violent crimes]. Some research suggests that the PCL-R may predict violent recidivism, but other work questions this assertion.4 I'm definitely not the expert here, so please weigh in if you have an opinion.

Returning to behavioral performance on the X/K response inhibition task, this did not clearly differentiate between those inmates who would reoffend after release from those who did not. So we cannot conclude that cognitive factors are related to nonviolent criminal reoffending,5 at least from this one experiment that evaluated one specific executive function.

Footnotes

1 There were nine participants arrested for violent offenses, and of these six were arrested for both violent and nonviolent offenses. These latter subjects were an inaccurate bunch (42% commission errors), but it's hard to make much of such a small group.

2 The significance went down further if you controlled for age at release (for instance).

Thursday, March 28, 2013

Is it possible for a brain scan to predict whether a recently paroled inmate will commit another crime within 4 years? A new study by Aharoni et al. (2013) suggests that the level of activity within the anterior cingulate cortex might provide a clue to whether a given offender will be rearrested.

Dress this up a bit and combine with a miniaturized brain-computer interface that continuously uploads EEG activity to the data center at a maximum security prison. There, machine learning algorithms determine with high accuracy whether a given pattern of neural oscillations signals the imminent intent to reoffend that will trigger deep brain stimulation in customized regions of prefrontal cortex, and you have the plot for a 1990s cyberpunk novel.

But we're getting way ahead of ourselves here...

Dr. Kent Kiehl outside the mobile scanner his group uses to look at the brains of inmates at New Mexico prisons. Credit: Nature News.

The actual study in question used functional MRI to scan the brains of 96 male inmates at two New Mexico state correctional facilities while they performed a cognitive task (Aharoni et al., 2013). The task required responding to a frequent stimulus presented 84% of the time ("X") and inhibiting responses to the rare stimulus ("K").

The major comparison examined brain activity on incorrect responses to "K" (commission errors) vs. correct responses to "X" (hits). This contrast was restricted to a region of interest (ROI) in the dorsal anterior cingulate cortex (dACC), which has been associated with a wide array of cognitive and emotional control functions (Posner et al., 2007).

Results from a separate group of 102 age-matched control participants (mean = 33.9 yrs) from Hartford, CT1 determined the a priori ROI, with the peak voxel located at coordinates x = −3, y = 24, z = 33 in the center of a 14 mm sphere. One control ROI was chosen in a more ventral and anterior region of medial prefrontal cortex (mPFC) at 0, 51, −6.

The most strongly activated voxel in the offender group for the error vs. hit contrast was remarkably close to the one determined from the independent sample and fell well within the a priori ROI (see blue crosshairs in figure below).

The dACC has been strongly implicated in error processing (Simons, 2010), and that was no different in the offenders as a group. Other regions significantly activated by commission errors included bilateral inferior frontal cortex/insula, fusiform gyrus, and cerebellum but these were not discussed.

Of greatest interest is whether this dACC activity can predict recidivism. For this the authors did a survival analysis:

First, a Kaplan–Meier survival function was computed to describe the proportion of participants surviving any felony rearrest over the 4-y follow-up period, ignoring the influence of any particular risk factor (Fig. S1). Cox proportional hazards regression was then used to examine (i) the zero-order effects of ACC activity on months to rearrest for any crime, (ii) the shared and unique influence of the ACC and other potential risk factors on months to rearrest for any crime, (iii) for nonviolent crimes, and (iv) the shared and unique influence of the medial prefrontal cortex (mPFC) control region and other potential risk factors on months to rearrest for any crime. ...

... A significant association was found whereby, for every one unit increase in ACC activity, there was a 1.39 (i.e., 1/exp[B]) decrease in the probability of rearrest.

...Meaning that the participants with greater ACC activity were less likely to reoffend. The mPFC ROI did not show this association. Then a median split divided the offender sample into high ACC and low ACC groups (survival function shown below).

Fig. 1 (Aharoni et al., 2013). Cox survival function showing proportional rearrest survival rates of high (solid green) vs. low (dashed red) ACC response groups for any crime over a 4-y period. Results of this median split analysis were equivalent to that of the parametric model: bootstrapped B = 0.96; SE = 0.40; P < 0.01; 95% CI, 0.29–1.84. The mean survival times to rearrest for the low and high ACC activity groups were 25.27 (2.80) mo and 32.42 (2.73) mo, respectively. The overall probabilities of rearrest were 60% for the low ACC group and 46% for the high ACC group.

So for all felonies (both violent and nonviolent), a substantial percentage of participants were likely to be rearrested within 4 years. The ACC classification scheme would wrongly condemn the 40% of low ACC parolees who did not reoffend, and would miss the 46% of high ACC parolees who did commit crimes after release. When you look at it that way, it's not all that impressive and completely inadmissable as evidence for decision-making purposes. For nonviolent felonies only, the probability of rearrest for high ACC offenders was 31%, compared to 52% for low ACC offenders.

A number of other variables were considered in the regression models (and singly as predictors), including age at release, drug and alcohol use, scores on the Psychopathy Checklist-Revised (PCL-R) (Hare, 2003), and commission errors. The best predictor was still ACC activity, but age and score on Factor 2 of the PCL-R both came in at around p=.05. On the PCL-R, Factor 1 includes callousness and the inability to experience remorse, guilt, and empathy while Factor 2 includes impulsivity, stimulation seeking, and irresponsibility (Ermer et al., 2012). The authors consider low ACC activity to be a manifestation of impulsivity, but it could just as easily be related to a lack of concern about making mistakes (i.e., irresponsibility).

Should functional MRI data be used in parole board hearings?

No, absolutely not. No one is suggesting this, not even Kiehl himself:

Kiehl isn’t convinced either that this type of fMRI test will ever prove useful for assessing the risk to society posed by individual criminals. But his group is collecting more data — lots more — as part of a much larger study in the New Mexico state prisons. “We’ve scanned 3,000 inmates,” he said. “This is just the first 100.”

Nonetheless, I was very impressed that fMRI and behavioral data were collected from 96 prison inmates. That's no easy feat. And the total sample size is now up to a staggering 3,000 inmates!!

Another striking aspect of this paper is that Aharoni and colleagues made their individual subject data available as an Excel spreadsheet that can be downloaded from the PNAS website as supplementary material (Download Dataset_S01, XLSX). It includes the ROI beta weights along with a number of demographic and performance variables.

In my next post, I'll present the results of some analyses that I've conducted, and what they might suggest about behavioral performance in the Go/NoGo task.

Footnote

1 The median income in Hartford is rather low, and 30% of the population lives in poverty. Although not explicitly stated, these participants might be matched to the criminal offenders for socioeconomic status. The mean years of education was not given for either group. One notable difference, however, is that the control group was 52% female while all the offenders were male.

For those of us who have at heart the establishment and advancement of comparative psychology as a science coordinate with physiology there is the clear duty to make our work eminently worthy of scientific recognition and reliance.

Yerkes was a keen observer of Psychology and a strong supporter of its importance as a natural science. Unfortunately, he also promoted eugenics in the 1910's and 1920's.

This prompted twocomments on my knee-jerk reaction to "eugenics". Has the term been rehabilitated, unbeknownst to me? Is it fortunate that Yerkes believed in the racial inferiority of African Americans, based on theculturally biased intelligence tests he developed (Yerkes, 1923)?

Is modern-day amniocentesis to screen fetal DNA for Down's syndrome and other (usually fatal) trisomies really the same thing as limiting immigration from specific countries based on the population's lower "intelligence" (as assessed by flawed tests)?

"Far more interesting doubtless to the practical eugenist than occupational differences in intelligence or specifications are the racial differences which appear when the foreign-born American draft is analysed into its principal constituent groups. The difference even of median score or letter grade distribution are so great as to be significant alike to the American people and to the eugenists of the world."

Recently on Twitter, evolutionary psychologist and provocateur Jesse Bering posed the question of whether a case could be made for modern-day eugenics. I originally thought he was being trollish, or perhaps had taken a page out of filmmaker Lars von Trier's comedy playbook (whose Nazi jokes got him banned from Cannes).

Since Bering is an openly gay man, I thought the question was especially preposterous. Who gets to decide the traits and "disorders" slated for elimination? But then I read the essay on Chinese eugenics by evolutionary psychologist Geoffrey Miller -- a response to the question WHAT *SHOULD* WE BE WORRIED ABOUT?

China has been running the world's largest and most successful eugenics program for more than thirty years, driving China's ever-faster rise as the global superpower. I worry that this poses some existential threat to Western civilization. Yet the most likely result is that America and Europe linger around a few hundred more years as also-rans on the world-historical stage, nursing our anti-hereditarian political correctness to the bitter end.

So the resurgence of interest in eugenics is serious? And not just among white supremacists?

The BGI Cognitive Genomics Project is currently doing whole-genome sequencing of 1,000 very-high-IQ people around the world, hunting for sets of sets of IQ-predicting alleles. I know because I recently contributed my DNA to the project, not fully understanding the implications.1 These IQ gene-sets will be found eventually—but will probably be used mostly in China, for China. Potentially, the results would allow all Chinese couples to maximize the intelligence of their offspring by selecting among their own fertilized eggs for the one or two that include the highest likelihood of the highest intelligence. Given the Mendelian genetic lottery, the kids produced by any one couple typically differ by 5 to 15 IQ points. So this method of "preimplantation embryo selection" might allow IQ within every Chinese family to increase by 5 to 15 IQ points per generation. After a couple of generations, it would be game over for Western global competitiveness.

What do you think, is the BGI Cognitive Genomics Project a menace to "Western civilization" as we know it? Or is Miller's scenario a fantasy contingent upon on a vast array of genetic information that is currently unavailable2.... or even unattainable in the foreseeable future?

"The average German physiologist uses very different tones of voice for the “Physiolog” and the “Psycholog.” Some of them apparently feel that psychology is too near akin to metaphysics to be a safe favorite for the natural scientist, while others are evidently satisfied in their own minds that the psychic is not and cannot be material of a natural science. In America too there is a strong prejudice against psychology, among the natural scientists especially, or, if not prejudice, there is a distrustful curiosity which makes the life of the truly scientific student of psychic reactions at times unpleasant. This general distrust and ridicule of psychology is doubtless due, first, to the fact that the naturalistic movement of the last century was accompanied by a wide spreading and deep distrust of the speculative sciences of which psychology was then, and is still by many, reckoned as one; and second, perhaps almost as largely, to the semi-scientific and too often carelessly used methods of that new psychology which called itself experimental."

-ibid

Yerkes was a keen observer of Psychology and a strong supporter of its importance as a natural science. Unfortunately, he also promoted eugenics in the 1910's and 1920's.

Friday, March 15, 2013

In case you missed it, I had a guest post this week in Nature's SpotOn NYC series on Communication and the Brain (#BeBraiNY), held in conjunction with Brain Awareness Week. The theme concerned the challenges of engaging the public's interest in cognitive sciences, and communicating the knowns (and unknowns) of brain disorders:

In the current funding climate of budget cuts and sequestration, there’s a wide latitude between overselling the immediate clinical implications of "imaging every spike from every neuron" in the worm C. elegans (as in the proposed Brain Activity Map Project) and ignoring science communication entirely, leaving it up to the university press office.

Who occupies the middle ground between the industry cheerleader and the disinterested academic? Science bloggers, for one. Scientist bloggers comprise a growing segment of the science communication world.

Many of us have been critical of how traditional media channels can distort the actual scientific results and mislead the public. With the mainstreaming of neurocriticism, I felt this topic had been discussed extensively in recent months, so I moved on to the responsibilities we face in presenting accurate information. Some examples were drawn from my posts on unusual neurological disorders, including Prosopometamorphopsia (a condition where faces look distorted on one side) and Othello Syndrome (delusional jealousy). Both posts can turn up on the first page of a Google search, so I do feel an obligation to be factual and informative.

Scientist bloggers serve an important function in the continuum of science communication. We should take our responsibility for presenting high quality, ethical information very seriously, to help stem the ongoing flood of neurocrackpottery.

Amidst the SpotOn NYC series extolling the virtues of science blogging came a new paper suggesting that science blogs are inferior sources of information relative to traditional media (Allgaier et al., in press):

Scientists may understand that neuroscience stories in legacy media channels are likely to be of higher quality than similar narratives found in blogs. Stories in social channels are often crafted on the fly, without the help of experienced editors who can point out holes in the narrative or who can insist on rewriting and revision. Blog posts also tend to be shorter narratives, bereft of the kind of complexity and nuance possible only in long-form journalism.

Obviously, there's a lot of high quality "long-form" journalism (which is never defined in the paper), but a huge number of high quality, complex and nuanced blog posts can be found as well. The passage above sparked quite the discussion on social media. Here's one initiated by respected journalist, blogger, and science writer Carl Zimmer:

I found passages like the one I just quoted [the one above] to be puzzling on many levels.

Science blogs pretty much came into existence as a way for scientists themselves to critique bad coverage in traditional media. And, ten years later, that remains a powerful tradition.

The paper presents a romantic, uncritical view of the press. Speaking as a journalist, I can say this is a view we can ill-afford.

What's more, neuroscience blog posts are very often deep, nuanced, and more accurate than "churnalism" driven by glib press releases.

If neuroscientists are indeed avoiding blogs for this reason (no data provided in the paper that this is true), then they are sadly misguided.

Eight others joined in the discussion, which is worth reading. One of the participants was Dominique Brossard, an author on the article in question.

In brief, Allgaier et al. (in press) randomly contacted 1,248 "productive" neuroscientists who had published at least 8 articles in the preceding 2-year period. The survey participation rate was 21.3% in the US and 32.6% in Germany.

The scientists responded to questions about three dimensions of public media channels, both traditional and online: (1) their personal use of these channels to “follow news and information about scientific issues”; (2) their assessment of the impact of scientific information in these channels on public opinion about science; and (3) their assessment of the impact of such information on “science-related decisions made by policymakers.” The respondents answered the questions with respect to a comprehensive list of traditional print or broadcast media, online analogs of those media channels, blogs, and content in social networks.

Respondents were primarily male (78%) and over 40 (79%). Is this a typical sampling of neuroscientists? Obviously not, since it is gender-imbalanced1 and excludes most grad students and the average post-doc.

The results in this group of participants suggested a preference for old media:

The results of our survey indicate that the respondents in both countries remained heavily reliant on journalistic narratives, in both traditional and online forms, for information about scientific issues. Only a modest number of the surveyed neuroscientists reported that they use blogs or social networks to monitor such issues.

Fig. 1a (modified from Allgaier et al., in press). Media use (in percentages) among neuroscientists in the United States and Germany. For the exact wording of the questions, detailed data, and significance information, consult supplemental table S1, available online at http://dx.doi.org/10.1525/bio.2013.63.4.8[not online as of this writing].

The over 40 crowd was more reliant on newspapers and valued online articles less than the younger set, who used social media more often as a source of popular science news. Women were less reliant on newspapers and printed pop sci magazines for science issue information than men.

Do we really know if the participants consider blogs and social media to be inferior sources of information for the reasons quoted above? We do not. The authors were speculating, as they were in this paragraph (which elicited howls in the Blogs versus journalism discussion):

Finally, we speculate that the scientists in this study may value journalistic narratives because they appreciate that journalism is indifferent to the interests and goals of science. Although this may be perceived as a disadvantage of journalism from the scientists’ point of view, it is actually a key advantage. Their role as external observers affords journalists credibility compared with scientific self-presentation.

This attitude is quite different from the skeptical neuroblogger view of mainstream science journalism, which is covered in many of the posts below. It seems to me that Allgaier et al.'s sampling method potentially excluded many of these voices, who were not considered "productive" neuroscientists by the authors.

Women have been an increasing force within the field, more than doubling over the past 20 years – 21 percent of SfN members were women in 1982 compared to 43 percent in 2011, according to membership surveys.

Neuroscience itself is actually quite new. Although the brain, behaviour and the nervous system have been studied for millennia the concept of a dedicated ‘neuroscience’ that attempts to understand the link between the brain, mind and behaviour only emerged in the 1960s and the term itself was only coined in 1962. Since then several powerful social currents propelled this nascent science into the collective imagination.

To me, those dates seem quite recent in relation to brain research that has been conducted for centuries. Was there no neuroscience research prior to the 60s? My general perception is that ‘neuroscience’ research has been around a lot longer than that, even if it wasn't called by that precise name. It might have been called psychobiology (Yerkes, 1921), neurobiology (Brodmann, 1909),1 neurophysiology (1938) or neurochemistry (Lewis, 1948), but the types of questions asked and the experiments performed appear to be in line with much of what passes as a dedicated neuroscience in modern times. Here's Dr. Nolan D.C. Lewis speaking at the 96th Annual Session of the American Medical Association, Atlantic City, NJ, June 13, 1947 (Lewis, 1948):

The actual nature of the thought processes is annoyingly elusive. What is the nature of thought? It is probably a manifestation of energy, but one can ask many questions about this. ... Do small areas of intact brain produce thoughts? Does the brain produce the mind independently or is it an instrument used by some other somatic processes or agents in the body? Does the brain itself think or is it a transmission center utilized by some other force? Is the mind the product of cerebral matter or is it dependent on something else which governs it? Can matter think? Either matter can produce mind or it cannot. Is mind a unique form of matter different from any other known forms of matter? While these questions and problems are probably not solvable by means of present technics, they are challenging, approachable and must eventually become elucidated if we are to get to the core of mental disorders.2

What's in a name?

I became curious enough to investigate whether the term ‘neuroscience’ was actually coined in 1962. @AliceProverbio confirmed that "Francis Schmitt used the term Neuroscience for the first time in 1962 to name his Neuroscience reserch group [at] MIT". I found the paper in the Journal of the History of Neurosciences that clearly recognizes the role of Schmitt, but it also opined that the word might have been invented earlier (Adelman, 2010):

...the word might have been coined by Ralph Gerard in the early 1950s...

Does it really matter when the word itself was first used? No, not for Vaughan's history of the birth neuroculture. I'm not going to get to the bottom of who should get credit, either. But I do find it interesting to see how the word is used in various historical contexts.

Not to be outdone by MIT, Harrison (2000) reviews the contributions and recollections of Five Scientists at Johns Hopkins in the Modern Evolution of Neuroscience, including those of pioneering neurophysiologist Professor Vernon Mountcastle:

‘In the 1940’s, and on, this place [Johns Hopkins University] was red hot for the development of Neuroscience’.

Noted historian of neuroscience Professor Stanley Finger, in his review on Women and the History of the Neurosciences, named several famous women neuroscientists of the 19th century (Finger, 2002):3

Women have been underrepresented in the early years of the neurosciences, much as they have been in other scientific endeavors. Nevertheless, the names of many important women contributors stand out if one begins in the latter part of the 19th century...

Two women, who worked in part with their husbands but also achieved greatness on their own as the 19th century drew to a close and the 20th century began, are Augusta Marie (Dejerine-) Klumpke (1859-1927), who was married to Joseph Jules Dejerine (1849-1917), and Cécile Mugnier Vogt (1875-1962), who was married to Oskar Vogt (1870-1950).
...

Three other famous women neuroscientists from the later period are Christine Ladd-Franklin (1847-1930), Maria MichailovnaManasseina (also known as Marie de Manacéine, (1843-1903), and Margaret Floy Washburn (1871-1939).

Ideally, Schmitt and his colleagues thought, the various physical, biological, and neural sciences could be brought together to attack a single goal, and what a goal — the ultimate one of all science and philosophy — how does the mind/brain work! Every field with some involvement in mind-brain studies would be included, from the molecular and subcellular areas of cell biology to the higher reaches of psychology and psychiatry. Such areas as cognitive psychology might not be able to contribute much to neurobiology; parallel fibers and psychophysical parallelism have little in common. But this field could pose major questions about higher brain function and the mechanisms of thinking, with molecular genetics perhaps providing answers about mechanisms operating at subcellular levels of the nervous system.

Ha, ha! So much for the modern convergence of brain and behavioral sciences...

2 It goes without saying that modern techniques have opened up new avenues of study. And that ethical standards for the proper conduct of human and animal research (e.g., The Purring Center in Cats) have improved considerably since then.

3 To be brutally obvious here, it bears repeating that the name of the journal in which this appears is the Journal of the History of the Neurosciences.

References

Adelman, G. (2010). The Neurosciences Research Program at MIT and the Beginning of the Modern Field of Neuroscience. Journal of the History of the Neurosciences, 19 (1), 15-23 DOI: 10.1080/09647040902720651

Sunday, March 10, 2013

Large black spots show points from which stimulation elicited purring. Small black spots show points in these sections which were stimulated without eliciting purring. Numerous other points in other sections were stimulated with negative results so far as purring was concerned (Gibbs & Gibbs, 1936).

In the course of a study which we conducted on the convulsion threshold of various parts of the cat’s brain, a region was found which when stimulated caused purring. This reaction was so striking and the region from which it was obtained so definitely localized that we consider it worthy of a special report.

Our experiments were conducted on 400 cats.

. . .

The points stimulated in our 400 experiments were fairly well scattered through the brain (Gibbs and Gibbs, ’36). In only three cases, however, did we obtain purring as a response to stimulation. In each this was the first response to weak stimulation; it was obtained with the secondary coil at 10 cm. or more from the primary. In all three cases the tip of the needle lay in the infundibular region (see figures).

CONCLUSION

Purring can be elicited by electrical stimulation in the infundibular region of the cat’s brain.

ADDENDUM (March 11 2013): Just to be crystal clear, the main reason the authors conducted the study in the first place was to determine seizure thresholds in different parts of the cat brain, not to find the purring center. They did not lay out the rationale for the seizure study in the purring paper, but see abstract below.

In this investigation we have attempted to determine the relative ease or difficulty with which convulsions can be produced by electrical stimulation of various parts of the cat's brain. The problem has significance because it bears directly on the question of whether or not a special part of the brain is concerned with the production of convulsions, a question of major importance to those interested in the etiology of epileptic seizures.

About Me

Born in West Virginia in 1980, The Neurocritic embarked upon a roadtrip across America at the age of thirteen with his mother. She abandoned him when they reached San Francisco and The Neurocritic descended into a spiral of drug abuse and prostitution. At fifteen, The Neurocritic's psychiatrist encouraged him to start writing as a form of therapy.